*Should `savePeople()` be unit tested?* Yes. You aren't testing that `dataStore.savePerson` works, or that the db connection works. You are testing that `savePeople` fulfills the promise it makes through its contract.

Imagine this scenario: someone does a big refactor of the code base, and accidentally removes the `forEach` part of the implementation so that it always only saves the first item. Wouldn't you want a unit test to catch that?

Put another way, you aren't testing that the functions it calls work, you're testing that it calls the correct functions.